Yesterday, actor Evan Rachel Wood launched a Twitter polemic against the ratings board in the US, the MPAA, for necessitating the removal of a scene where her character in Charlie Countryman receives oral sex. The edit was presumably made so the film avoids the NC-17 rating that would effectively bar it from many mainstream cinemas.

It's a microcosmic example of a much wider issue: cunnilingus is de facto arthouse. Even coming from the surprisingly stilted world of intra-male sex chat, it's clear that among my twentysomething peers this is a thoroughly mainstream, necessary part of modern sex – ignoring the fact that most men thoroughly enjoy it. And yet Hollywood, with its lumbering moral turning circle, hasn't come round to the idea.

It's generally used as a weighty stand-in for something other than "isn't oral sex good", be it po-faced male devotion, or female exoticism. A classic recent example is The Counselor, Ridley Scott's highbrow car crash, which opens with Michael Fassbender's character performing it on his girlfriend, played by Penelope Cruz. It's a change from Cormac McCarthy's original script, in which Cruz's character requests "finger-fucking". Instead of this real-life raunch, cunnilingus swings in to become the ultimate signifier of devotion and masculinity. Look – he even goes down on his lover, and he's still not emasculated! The woman receiving this kind of film pleasure is not having fun, but being blessed and anointed somehow. In Hollywood, if a woman receives oral sex, she's a Madonna; if she gives it, she's a whore.

Compare it with films that use cunnilingus purely as a sex act: Basic Instinct, which cut its scene for censors, and Blue Valentine, which was subjected to an NC-17 rating for not doing so. The latter provoked a disgusted reaction from producer Harvey Weinstein, who compared it with the lower R-rating for Piranha 3D: "A penis got coughed up in the movie by a piranha!" An image of anti-female body horror and castration anxiety if ever there was one, if you like to read into your B-movies.

There are other some choice examples, but they're few and far between. One memorable moment is the calm, unhurried scene in Monster's Ball between Billy Bob Thornton and Halle Berry's characters – director Marc Forster says in the DVD commentary that he included it because "you see the opposite, but never a man going down on a woman". Chasing Amy, meanwhile, has its naturalistic credentials massively improved by an honest discussion of cunnilingus (it also means Ben Affleck has starred in both the best and worst cunnilingus scenes ever).

Weirdly though, it mostly ends up being trashier films that tackle it - sorry - head on, though their treatment is inevitably freighted with laughs. American Pie's sequel features it as - not inaccurately - being key to satisfying the women the characters are chirpsing, while Scary Movie features a man finally pleasuring his previously coy girlfriend – but not before attending to her with a hedge trimmer, and retching. But at least it's featured – it's conspicuous by its absence elsewhere, and even more so when you consider the ubiquity of the blowjob. This is arguably the trickle-down (again, sorry) effect of an industry dominated by men who still find women strange, even disgusting.

So what will it take to normalise oral sex - or as much as the bizarro world of Hollywood sex could allow? Perhaps we can look to the world of rap music for some lessons. As this brilliant essay from Madeleine Holden shows, rap used to be all "Don't eat the pussy and play these hoes" and now it's Lil Wayne promising to "turn that thing into a rainforest, rain on my head, call it brainstorming." As Holden says, while there's been an adjustment period of rappers showing off how brave they are for going down on women, Lil Wayne has shifted the culture: "That stance changed the whole game, and all of a sudden rappers had permission to reveal their penchants for pussy-licking; to expose the reciprocal and mutually-rewarding sex they were probably having all along."

The more film-makers that feature oral sex as normal and non-symbolic, the less hostile it becomes for the MPAA – and the more it'll be embraced by culture more generally. There's surely a silent majority of adults who would rather see two characters love one another than a piranha choking up a penis.